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| Calcium crystals |
The other day I was reading
an article about using an egg drop activity to teach engineering to kindergarten
students, based on the a design process derived from the Engineering is Elementary (EIE) curriculum, developed by the Boston
Science museum. Though EIE does not have a specific egg drop activity, this is a good series for introducing engineering in elementary school. The article mentioned
putting one of the eggs in vinegar to show that there was a chemical
reaction. This chemical reaction
activity in the article was really just bolted onto the egg drop and not really
scaffolded for K students, but it did remind me of an activity I hadn’t done in
a while – making calcium crystals from dissolved egg shells.
This activity is pretty
simple. All you need is a washed, empty
eggshell; some plain, white vinegar; a glass tumbler to hold the dissolving
shell, and a pie plate or other broad, flat dish for growing your crystals. I
took an eggshell from my breakfast, washed it out with water, and put it in an
old jelly glass. I broke mine into smaller pieces so it would react and
dissolve faster. Then I poured on enough plain white vinegar to cover it. Any vinegar should work, but plain vinegar
will make it easier to watch the reaction.
As soon as you pour the
vinegar over the eggshell, you’ll see carbon dioxide bubbles coming off the
shell as the acid reacts to the shell’s calcium carbonate. After a couple of
days, a white inner coating from the shell will slide off and you can discard
it. Let the shell sit in the vinegar for about 5-7 days until it is mostly
dissolved. Once you are down to just a few fragments, you then run it through a
fine kitchen strainer or even a coffee filter to take out those remaining bits
of shell. Pour the vinegar-calcium solution into a pie pan or some other
broad shallow dish so it will evaporate quickly. You’ll get better crystals
if you let it evaporate slowly. I put mine in a closet and left it for
another week or so until it is all evaporated. These are the crystals I
got in the photos.
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| Pie plate for evaporation |
This can definitely lead
to a whole new set of investigations about crystal and all the ways you can make crystals with
household stuff.
This activity is pretty
simple. All you need is a washed, empty
eggshell; some plain, white vinegar; a glass tumbler to hold the dissolving
shell, and a pie plate or other broad, flat dish for growing your crystals. I
took an eggshell from my breakfast, washed it out with water, and put it in an
old jelly glass. I broke mine into smaller pieces so it would react and
dissolve faster. Then I poured on enough plain white vinegar to cover it. Any vinegar should work, but plain vinegar
will make it easier to watch the reaction.
As soon as you pour the
vinegar over the eggshell, you’ll see carbon dioxide bubbles coming off the
shell as the acid reacts to the shell’s calcium carbonate. After a couple of
days, a white inner coating from the shell will slide off and you can discard
it. Let the shell sit in the vinegar for about 5-7 days until it is mostly
dissolved. Once you are down to just a few fragments, you then run it through a
fine kitchen strainer or even a coffee filter to take out those remaining bits
of shell. Pour the vinegar-calcium solution into a pie pan or some other
broad shallow dish so it will evaporate quickly. You’ll get better crystals
if you let it evaporate slowly. I put mine in a closet and left it for
another week or so until it is all evaporated. These are the crystals I
got in the photos.
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